allocSimpleConfig should take a timeout parameter, and timeouts should be optional

[edsko]

At the moment, allocSimpleConfig hardcodes the TimeManager timeout to 30 seconds:

http2/Network/HTTP2/H2/Config.hs

Line 20 in b8f2268

timmgr <- T.initialize $ 30 * 1000000

This should instead be a parameter, and that parameter should not be of type Int, but rather of type Maybe Int: not applications want to impose timeouts between messages sent/received. For example, when running gRPC over HTTP2, it's entirely conceivable that there might be very long time intervals between messages on an open connection. Indeed, these intervals could be an hour or longer, which means that on 32-bit systems at least there is no appropriate value that can be passed to System.TimeManager.initialize that would work.

I will open a corresponding ticket also in http2-tls.

[edsko]

@kazu-yamamoto I'm not entirely sure yet if I am blocked on this; on 64-bit machines at least I can workaround the problem of not having optional timeouts by initializing my own TimeoutManager with a really high timeout. I will get back to you.

If it turns out I am blocked on this, I am happy submit a PR with a fix, but in the case I guess we need to think about what a suitable design would be.